Many electronic, optoelectronic, sensoric and micromechanical components have as a component silicon in doped and/or non-doped, crystalline and/or polycrystalline and/or amorphous form. In order to fulfill the component-specific requirements, silicon, may consequently be accordingly processed, which frequently includes a structuring of the silicon.
In general, a mask made of photoresist is made for the structuring of silicon, by means of which the removal by means of an etching process is controlled. In order to produce small structures by means of a photoresist mask, the photoresist may be exposed with an exposure mask having correspondingly small structures. In the range below the customary light wavelengths which are available for the exposure of the photoresist this may be possible with increased expenditure. However, structures with structural elements with a high aspect ratio are frequently used, i.e. the depth or height of the structural elements is large as compared with their lateral dimensions. If recesses and thus also elevations with nanodimensions with an aspect ratio of e.g. 2 are used on a silicon surface, a local removal of material may be carried out, which results in a recess of e.g. 200 nm with a lateral dimension of 100 nm. Consequently, the photoresist mask may also be produced with a comparable lateral dimension in an etching process on the basis of a photoresist mask and, moreover, it may have the necessary etching selectivity in order to also achieve the desired aspect ratio during the subsequent silicon etching process. Alternatively, high-resolution masks are also written with the aid of an electron beam (e-beam). These solutions have certainly a lot of uses, however, they also are very expensive. Consequently, constant efforts are made to find alternative processes which also make the structuring in the nanometer range possible.
However, in many conventional processes no high aspect ratio of the nanostructures is achieved, in particular if a low defect density is also desired. Thus, in the prior art, the nanostructure has typically an increased contamination density after production, i.e. undesired impurities on the surface and/or an increased number of crystal defects, if, at the beginning, monocrystalline silicon with a low crystal defect density was present. Consequently, these known processes can only be used in a restricted fashion or with poorer results in view of the total power behavior of the component. In some of these conventional processes plasma-aided processes with reactive ions on the basis of SF6 (sulphur hexafluoride) and oxygen, which are also known as RIE processes, were used for the microstructuring using the self-organization for the production of structured silicon surfaces, the metal particles ensuring the micromasking and, thus, the structure formation, cf. WO-A 02/13279, U.S. Pat. No. 6,091,021 and U.S. Pat. No. 6,329,296.
A disadvantage of this process consists in the use of metals in the plasma, which may result in an undesired contamination of the silicon. The detrimental influences of the slightest metal traces in the semiconductor production process, in particular in integrated circuits, are known. In addition to the contamination effect of the RIE facilities due to the admixture of metal, the extra cost and effort of these processes for a use in production processes needing a high yield and low process costs may be assessed as being disadvantageous.
Due to the process engineering difficulties in the conventional production of structured surfaces and their further processing an application of nanostructures in components such as sensors, optoelectronic components and the like in an inexpensive and reliable fashion thus has not been common so far.